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A WIFI MESH WIRELESS SELF-ORGANISING NETWORK RADIO TV TRANSMITTER in a small weather-proof case that fits into the centre of an obsolete satellite-dish, each node additionally broadcasting analogue 88.0MHz 0.2W FM radio and channel 37 UHF TV. The digital standards are 16kbitMono Audio - xvid 320x240pix 80kbit video - 802-11b wifi peers.

Saturday, December 27, 2008

The story of Moko the Dolphin - Whale Rescue

Bottlenose Dolphins sometimes shows curiosity towards humans in or near water. Occasionally, Bottlenose Dolphins have rescued injured divers by raising them to the surface. This is similar to behaviour they show towards injured members of their own species. In November 2004, a more dramatic report of dolphin intervention came from New Zealand. Four lifeguards, swimming 100 m (328 ft) off the coast near Whangarei, were approached by a shark (reportedly a Great White Shark). A group of Bottlenose Dolphins, most likely sensing danger to the swimmers, herded them together and tightly surrounded them for forty minutes, preventing an attack from the shark, as they returned to shore.

Dolphins have also been documented exhibiting altruistic behaviour toward other sea creatures. On Mahia Beach, New Zealand on March 10, 2008 two Pygmy Sperm Whales — a female and calf — became stranded on the beach. Rescuers, including Department of Conservation officer Malcolm Smith, attempted to refloat the whales, however their efforts failed four times. Shortly before the whales were to be euthanized a playful Bottlenose Dolphin known to local residents as Moko arrived and, after seemingly communicating with the whales, led them 200 meters along a sandbar to the open sea.

The two pygmy sperm whales were stranded on a sandbar at Mahia Beach, NZ

Rescuers watched as the dolphin guided the mother and calf to open sea

Moko the dolphin had already won over humans at Mahia Beach, where she plays with swimmers in the New Zealand surf and pushes kayaks along.

'Moko', a female dolphin that has been visiting the coastline around the Mahia Peninsula since March 2007, has attracted attention from locals and visitors who have been delighted by close encounters with the animal.

Moko the Mahia dolphin

Dolphins are wild animals

For people lucky enough to get close to dolphins, it is easy to be fooled by their sleek beauty and intelligence into thinking of them as pets rather than wild animals.

Approaching these marine mammals as if they are domesticated animals is a mistake that holds dangers for people and for dolphins. Following a few commonsense rules will result in a healthy environment for the dolphins and rewarding experiences for people who enjoy their company.

How can you help Moko?

Swimmers

Ensure that children are well supervised when in the water near Moko.

DO NOT:

try to handle Moko or any other dolphin.

surround the dolphin – always allow it to have an escape route where it can safely move to deeper water.

attempt to ride or be towed by a dolphin.

If you are approached by Moko when swimming, remain calm and let the dolphin make contact with you if it wishes to. Do not attempt to control Moko by chasing or pulling on her and when she chooses to leave, do not attempt to stop her.

Boaties

The other major threat to dolphins that interact with people is boat strike. The Marine Mammal Protection Regulations provide common sense rules for boaties to minimise the danger to dolphins.

General rules to follow when boating near dolphins:

Operate your boat slowly and quietly.

Manoeuvre your boat sensitively near dolphins. Do not obstruct their path, cut through a group or separate mothers from calves.

Avoid sudden noises that could startle the animals.

Keep the ocean clean by carefully disposing of any rubbish. Plastic waste can be particularly hazardous when discarded near waterways or beaches.

Keeping you and Moko safe

Dolphins have delicate skin that can be easily damaged when people touch them. They may carry diseases that can be transferred to humans and likewise, people with infections may cause dolphins to become unwell.

Dolphins are large, strong and agile and can injure people who get too close. World-wide, there has been one case recorded of a dolphin attacking and killing a person, something that happened after long and repeated provocation.

Due to their size and strength, 'playful' dolphins that choose to approach humans have been known to cause painful injuries to people. Injuries have included cracked ribs, internal damage and painful bruises. No matter how strong or speedy humans may be on land, compared with dolphins we are all slow and weak when in water, and have been described as having the power and agility of 'a slug on a carpet'. Avoiding a large fast marine mammal can be an impossible task.

Dolphins can also discriminate between 'favoured' and other humans and may physically chastise people they don’t like or try to stop 'playmates' from leaving the water. Some solo dolphins have been known to poke humans with their beaks and occasionally hold people under water for short periods. If dolphins become frightened or frustrated, they may injure people who crowd in around them by biting, butting or just trying to swim to open water.

If a dolphin interacts with you in a way that you don’t like, remain calm and swim to shore as soon as you are able. If the dolphin tries to block you or push you out to sea, persist, push it away, swim round it or call someone else over to distract it.

Do not give toys to a dolphin

Playing with items may result in injury to the dolphin at a later date. If it associates items such as crayfish floats with play, it may approach all floats as toys and can then become entangled in ropes or set nets. Entanglement in fishing gear is one of the biggest threats faced by dolphins.

Dolphins can also seem aggressive when they attempt to take items that they think are toys, such as diving masks, cameras, boogie boards or fins. In any battle for possession between dolphins and humans, it is most likely that people will lose their gear. For the dolphin, there are dangers if it approaches other objects in the ocean as if they are toys, with potential for entanglement, choking and other major injuries caused by 'playing' with rubbish.

Avoid wearing suntan lotion

Dolphin facts

Bottlenose dolphins earn their name from the shape of their short, stubby beak. Their lower jaw also projects beyond the upper, giving them the appearance of wearing a permanent grin.

They are often seen along the East Coast, usually in groups of up to 30 animals.

Males are larger than females and can be as long as 4 metres and weigh up to 300 kg.

They have little or no sense of smell, but make up for it with a sharp sense of hearing. They have excellent vision in and out of the water.

The brain of a bottlenose dolphin is larger than a human brain, but the area concerned with intelligence is smaller. Their skin is smooth and feels sort of like an inner tube.

Bottlenose dolphins swim at speeds of about 5-11 kilometres, using their flippers to steer, and with the help of their flukes, to stop.

All dolphins have to be conscious to breathe air but they also need to sleep. Bottlenoses let one half of their brain sleep at a time so they can rest without drowning and can hold their breath for up to 20 minutes.

Bottlenose dolphins communicate in several different ways. They squeak and whistle and use body language – leaping as high as 5 metres in the air, snapping their jaws, slapping their tails on the surface of the water and even butting heads. They have great flexibility because they have fewer fused vertebrae in their necks than other dolphins.

Females give birth every 2 to 3 years, normally 1 calf after a pregnancy of 1 year. The calves are usually born tail first so they don’t drown. When first born, its mother will whistle to it over and over again until it can repeat her whistle. The calf can then always find its mother.

Bottlenoses will eat almost any kind of fish. Their diets also include squid and small crustaceans such as shrimp. They swallow their food whole and catch fish with 18-26 pairs of sharp cone-shaped teeth on each side of their jaws.

Its important to remember that bottlenose dolphins can be unpredictable and aggressive - to each other and to other animals, including humans. As wild animals please give them the respect they deserve.

A dolphin has come to the rescue of two whales which had become stranded on a beach in New Zealand.

Conservation officer Malcolm Smith told the BBC that he and a group of other people had tried in vain for an hour and a half to get the whales to sea.

The pygmy sperm whales had repeatedly beached, and both they and the humans were tired and set to give up, he said.

But then the dolphin appeared, communicated with the whales, and led them to safety.

The bottlenose dolphin, called Moko by local residents, is well known for playing with swimmers off Mahia beach on the east coast of the North Island.

Mr Smith said he gave the dolphin a pat to say thank you

Mr Smith said that just when his team was flagging, the dolphin showed up and made straight for them.

"I don't speak whale and I don't speak dolphin," Mr Smith told the BBC, "but there was obviously something that went on because the two whales changed their attitude from being quite distressed to following the dolphin quite willingly and directly along the beach and straight out to sea."

He added: "The dolphin did what we had failed to do. It was all over in a matter of minutes."

Back at play

Mr Smith said he felt fortunate to have witnessed the extraordinary event, and was delighted for the whales, as in the past he has had to put down animals which have become beached.

He said that the whales have not been seen since, but that the dolphin had returned to its usual practice of playing with swimmers in the bay.

"I shouldn't do this I know, we are meant to remain scientific," Mr Smith said, "but I actually went into the water with the dolphin and gave it a pat afterwards because she really did save the day."

How Moko the dolphin gave humans a masterclass in saving stranded whales

Moko the dolphin had already won over humans at Mahia Beach, where she plays with swimmers in the New Zealand surf and pushes kayaks along with her snout.

Now the friendly bottle-nosed has shown her empathy for other species, by saving two whales from almost certain death after they became stranded.

Human attempts to guide the two pygmy sperm whales through a narrow escape route from the beach had consistently failed, and all seemed lost until the dolphin intervened.

Moko, a regular visitor to Mahia Beach on the east side of North Island, appeared to communicate with the whales before guiding them to open water.

Malcolm Smith, a field worker for the New Zealand Department of Conservation, said that he had almost given up and was contemplating killing the whales to prevent further distress, until Moko arrived.

“It was amazing,” he said. “It was like she grabbed them by the flipper and led them to safety. We worked for over an hour to try to get them back out to sea . . . but they kept getting disorientated and stranding again.”

The whales — a three metres (10ft) long female and her 1.5-metre male calf — had been unable to negotiate a sand bar that was blocking their way to deeper water.

Mr Smith was alerted to the whales’ plight early on Monday morning by a neighbour. “Over the next hour and a half I pushed them back out to sea two or three times and they were very reluctant to move offshore,” he said.

“I was reaching the stage where I was thinking, it’s about time to give up, I’ve done as much as I can. The whales were getting tired and I was getting cold when Moko turned up. She just came straight for us and escorted the two whales along the beach and out though the channel.”

He heard Moko and the whales making noises before they departed, he said. “The whales were on the surface of the water quite distressed. They had arched their backs and were calling to one another, but as soon as the dolphin turned up they submerged into the water and followed her.”

Moko led the whales 200m along the beach and once they reached the end of the sand bar, Moko turned a right angle through a narrow channel and led the whales to safety.

Rescued whales often return to the site of their stranding, but Moko’s actions appear to have had long-term success. “She obviously gave them enough guidance to leave the area because we haven’t seen them since,” Mr Smith said.

“What the communication was I do not know, and I was not aware dolphins could communicate with pygmy sperm whales.”

Mark Simmonds, director of science at the Whale and Dolphin Conservation Society, said that bottle-nosed dolphins are renowned for their ability to empathise with humans and other animals. “The whole notion that a bottle-nose dolphin would have shown the whales the way out is completely possible,” he said.

“Dolphins have got the ability to plan, to think ahead, to persuade others to take part. They almost certainly do not have a common language with pygmy sperm whales, but they would understand that the whales would have been at risk of stranding. The first thing a dolphin does when it has a calf is to push it to the surface so it can breathe.”

Dolphins are known to swim in mixed groups with some species of whale to protect themselves from predators, so it may not have been unusual for the animals to associate with one another, he said. He is aware of one instance of a bottle-nosed dolphin — nicknamed Dave by locals in Folkestone, Kent, where the female creature is a regular sighting — playing with a seal.

Moko has become famous for her antics at Mahia, which include playing in the surf with swimmers, approaching boats to be patted and pushing kayaks through the water with her snout. Once she had assisted the whales she immediately returned to the beach to play with local residents.

Such close interaction with humans is rare among dolphins but not unknown. Mr Smith said: “She’s become isolated from her pod obviously for one reason or another, but made Mahia home just at the moment.”

Up to 30 whales become stranded on Mahia Beach every year, most of which have to be put down.

“I don’t know if next time we have a whale stranding we can get her to come in again. She certainly saved the day for us and the whales this time.”

The flip side

— Todd Endris, a Californian surfer, was saved by a pod of bottle-nosed dolphins last year after an 18ft great white shark attacked him in Monterey Bay. The 24-year-old was hurled from his board and bitten in the chest and stomach. As the shark began swallowing his leg the dolphins slapped their tails and formed a protective ring around the surfer, allowing him to paddle to shore

— The US Navy’s marine mammal programme investigates the military uses of dolphins — officially concentrating on their ability to detect undersea mines. The Soviet Union was believed to train killer dolphins to attack enemy frogmen and launch suicide-bomb attacks against warships. In 2000, after funding for the Russian programme was cut, many of the dolphins were reportedly sold to Iran

— Researchers at Southern Cross University in Australia studying dolphin communication recorded almost 200 distinct sounds used during feeding, migration and socialising. They were so “complex and contextual” that the researcher suggested they amounted to a basic language

— Pliny the Younger, a Roman official and writer, tells the tale of a boy who rode on the back of a dolphin, to the delight of his village. The boy and dolphin became a sensation and “all the magistrates round flocked hither to view this sight”. But soon, Pliny says, “the quiet and retirement of the place was utterly destroyed” and the decision was taken to kill the dolphin

— Amazonian dolphins impress potential mates by carrying clumps of weed on their fins or sticks in their mouths. The behaviour, distinct from that of other dolphins, supports the idea of “dolphin culture” — behaviour that is learnt from peers rather than instinctive

USA swines pollute for private profit

A large volume of fly ash slurry was released on December 22, 2008, when an earthen dike broke at a 40 acre (16 hectare) waste retention pond at the Tennessee Valley Authority's Kingston Fossil Plant in Roane County, Tennessee, USA. Over 1 billion gallons of coal fly ash slurry was released. The coal-fired power plant, located in the city of Kingston, uses three ponds to store fly ash, a byproduct of coal combustion, in wet form. The slurry (a mixture of fly ash and water) traveled downhill, covering up to 400 acres (160 ha) of the surrounding land, damaging homes and flowing into nearby waterways such as the Emory River and Clinch River (tributaries of the Tennessee River). It was the largest fly ash slurry spill in United States history.

An aerial view shows workers standing near a home that was destroyed when a retention pond wall collapsed at the Tennessee Valley Authorities Kingston Fossil Plant, Monday, Dec. 22, 2008 in Harriman, Tenn. The Tennessee Valley Authority says the 40-acre pond held a slurry of ash generated by the coal-burning Kingston Steam Plant.

An aerial view shows homes that were destroyed when a retention pond wall collapsed at the Tennessee Valley Authorities Kingston Fossil Plant, Monday, Dec. 22, 2008 in Harriman, Tenn. The Tennessee Valley Authority says the 40-acre pond held a slurry of ash generated by the coal-burning Kingston Steam Plant.

Mon Dec 22, 1:06 PM ET

An aerial view shows workers standing near a home that was destroyed when a retention pond wall collapsed at the Tennessee Valley Authorities Kingston Fossil Plant, Monday, Dec. 22, 2008 in Harriman, Tenn. The Tennessee Valley Authority says the 40-acre pond held a slurry of ash generated by the coal-burning Kingston Steam Plant.

The TVA and Environmental Protection Agency initially estimated that the spill released 1.7 million cubic yards (1.3 million cubic metres) of sludge, then on December 25, 2008 more than tripled that estimate to 5.4 million cubic yards (4 million m³) following an aerial survey. The spill covered surrounding land with up to six feet (2 m) of sludge. The EPA estimated that it will take four to six weeks to clean up; however, Chandra Taylor, the staff attorney for the Southern Environmental Law Center, stated that the cleanup could take months and possibly years.

The 40-acre (16 ha) unlined aboveground pond was used to contain a watery slurry of fly ash generated by the burning of finely ground coal at the steam power plant. The fly ash, which is the consistency of face powder, comprises the fine particulate pollutants produced by the combustion of coal, which are collected rather than allowing them to escape into the atmosphere, then mixed with water so they can be pumped into the retaining pond. Once the particulate matter settles out, it is moved to other, drier ponds. The pond was surrounded by 60-foot (20 m) tall earthen walls, which had developed leaks on two occasions since 2002. Although the land surrounding the power plant is largely rural rather than residential, the spill caused a "tidal wave" of water and ash that covered 12 homes, pushing one entirely off its foundation and rendering three uninhabitable. It also washed out Swan Pond Road, ruptured a major gas line, and temporarily disrupted power lines, though power was restored quickly. Though 22 residences were evacuated, nobody was reported to be injured or in need of hospitalization. It was the largest coal slurry spill in United States history, approximately 1.5 times the size of the Martin County sludge spill of 2000, which spilled 306 million US gallons (1.2 million m³) of liquid coal waste. The sludge was enough to fill 1,660 Olympic-size swimming pools, and the amount released was approximately 50 times larger than the 1989 Exxon Valdez oil spill. On December 23, 2008, a TVA spokesman, Gil Francis Jr., stated that, at the time of the spill, the area contained approximately 2.6 million cubic yards (2.2 million m³) of ash, and that two-thirds of that had been released.The New York Times noted that the amount spilled is larger than the amount stated to have been in the pond before the spill, a discrepancy the TVA was unable to explain. The containment area affected was one of three; the other two stayed intact, while only the retaining wall for the 40-acre (16 ha) pond was affected.

The spill killed a huge number of fish. Although residents feared water contamination, early tests showed that the public water supply met drinking water standards. A test of river water near the spill showed elevated levels of lead and thallium, and "barely detectable" levels of mercury and arsenic.

Rain totaling 4.9 inches (124 mm) over the course of the month of December and 14 °F (−10 °C) temperatures were stated as having contributed to the cause of the spill. A report dated from October 2008 had found a "minor leak" present in the faulty wall, though the report was not finalized. Local residents said that the spill was not a unique occurrence; the 1960s-era pond had been observed leaking slurry to a lesser degree, and being repaired, nearly every year since 2001. A TVA release confirmed that there had been two prior cases of seepage, in 2003 and 2006.

Response

TVA spokesman Gil Francis Jr. said that the TVA was "taking steps to stabilize runoff from this incident." In response to a video that showed dead fish on the Clinch River, which had received runoff from the spill, he stated "in terms of toxicity, until an analysis comes in, you can't call it toxic." He continued by saying that "it does have some heavy metals within it, but it's not toxic or anything." Chandra Taylor, an attorney with the Southern Environmental Law Center, called this statement irresponsible, claiming that coal was naturally toxic and therefore the fly ash waste product contained concentrated amounts of mercury, arsenic and benzene. She added, "These things are naturally occurring, but they concentrate in the burning process and the residual is more toxic than it starts." Nevertheless, due to pressure exerted in 2000 by utilities, the coal industry, and Clinton administration officials, fly ash is not strictly regulated as a toxic pollutant by the EPA. Residents and environmental groups expressed concern that the fly ash slurry could become more dangerous once it dries out, but have as yet received no information about this from the TVA.

Meanwhile, the EPA and Tennessee Department of Environment and Conservation awaited the results of soil and water testing to judge their response, while the Tennessee Emergency Management Agency promised to put up barriers to stop the ash from reaching the Tennessee River. By early on December 24, 2008, a flyover by The New York Times showed no evidence of any barriers having been erected, although they did note repair work being done on the nearby railroad, which had been halted by the spill when 78,000 cubic yards of sludge covered tracks. By the afternoon of that day, dump trucks were being used to deposit rock into the Clinch River to prevent the further downstream contamination. The TVA has also slowed river flow, for the same purpose.

Lisa Evans, an attorney for Massachusetts-based environmental group Earthjustice, spoke out against the government, accusing them of lax regulations on the issue. She also blamed the industry for ineffective safeguards, citing other similar cases. She stated that "The saddest thing is this is entirely avoidable. These people in these communities don't have to be in harm's way. This is not some complicated problem like nuclear waste. This is something the utilities know how to do." Thomas J. FitzGerald, the director of the environmental group Kentucky Resources Council and an expert on coal waste, told The New York Times that the ash should have been buried in linedlandfills to prevent toxins leaching into the soil and groundwater (as recommended in a 2006 EPA report), and stated that "I find it difficult to comprehend that the State of Tennessee would have approved that as a permanent disposal site." Concern has also been expressed by environmental groups and local residents that no warnings were issued to residents living in the area about the potential dangers of the site. The site may be slated as a Superfund site, although no decision regarding this has yet been made. The environmental group Greenpeace asked for a criminal investigation into the incident, focusing on whether the TVA could have prevented the spill.

TVA president Tom Kilgore said that, in light of the spill, the Authority would consider switching the Kingston plant over to "dry" byproduct methods, which would reduce the chances of another spill. Five TVA-operated plants use this method, while Kingston and another five use a "wet" process. The power plant continues to operate, with waste being sent to one of the two remaining intact containment ponds.

The Tennessee Department of Environment and Conservation will be monitoring for potential chronic health effects to the community.

Monday, December 22, 2008

Frequencies - transmitters

The World Above 30 MHz

Since VHF and UHF propagation is usually "line of sight," frequency allocations and usage are far more "localized" on frequencies above 30 MHz. However, there are some broad allocations for different purposes used in the United States and most of the rest of the Americas. The following is a summary of the main frequency bands found above 30 MHz. Please remember that listening to cellular phones, cordless phones and wireless intercoms is illegal in the United States.

30 to 50 MHz: This is known as the "VHF low" band. Most transmissions will be in narrow band FM with channels spaced at 20 kHz intervals. A wide variety of stations can be heard on this range, including businesses, federal, state, and local governments, law enforcement agencies, and various industrial radio services.

50 to 54 MHz: This is the six-meter ham radio band. The first megahertz is mainly used for USB, AM, CW, FSK modes, digital modes. The remainder of the band is used for narrow band FM, both simplex and through repeaters. 52.525 MHz is widely used as a simplex and calling frequency.

54 to 72 MHz: Television channels 2, 3, and 4 are located in this range. The video portions will sound like distorted noise on a scanner. The audio portions are in FM, but will sound "clipped" and "tinny" unless your scanner can tune this range in wide band.

72 to 76 MHz: This range is used for remote control signals for model airplanes and garage door openers, wireless microphones (including those used by law enforcement agencies), and two-way communications inside factories, warehouses, and other industrial facilities. Most channels are spaced at 20 kHz intervals.

76 to 88 MHz: This range is used for television channels 5 and 6.

88 to 108 MHz: This is where the FM broadcasting band is located.

108 to 136 MHz: This band is used for civilian aeronautical communications and all transmissions are in AM. Aeronautical beacons occupy 108 to 118 MHz; these continuously transmit a station identification and are used for navigation. The rest of the band is used for traffic between aircraft and air traffic control towers on channels spaced at 25 kHz intervals.

136 to 138 MHz: This segment is mainly used by weather satellites to transmit photographic images.

138 to 144 MHz: The various military services are the biggest users of this segment in the United States, with most transmissions in narrow band FM and spaced at 5 kHz intervals. You can also hear ham radio operators who are members of the military affiliate radio service (MARS).

144 to 148 MHz: This is the two-meter ham radio band. This is the most heavily used ham radio band in the United States. USB and various FSK modes are mainly used in the first 500 kHz, and the rest of the band is FM. Most activity is through repeaters, although simplex activity is found on frequencies like 146.52 MHz. For more information about this band, visit the ham radio section of this site.

148 to 150.8 MHz: The usage here is similar to the 138 to 144 MHz range.

150.8 to 174 MHz: This is known as the "VHF high" band, and it is used by the same wide spectrum of users as the 30 to 50 MHz band.

174 to 216 MHz: This range is used for television channels 7 through 13.

216 to 220 MHz: In the United States, this band is used by the automated maritime telecommunication system (AMTS) used on major inland waterways such as the Great Lakes and the Mississippi river. Communications are in FM on channels spaced at 12.5 kHz intervals. However, the 219 to 220 MHz range is shared with ham radio. On this range, ham stations can be used to relay digital messages to other hams, subject to a maximum power of 50 watts. Hams must first register to use their shared allocation, and cannot use it within range of maritime users.

220 to 222 MHz: This range was reallocated a few years ago from ham radio to land mobile radio. Frequency usage and modulation have not yet been finalized, although new narrow bandwidth modes are expected to be used.

222 to 225 MHz: This is the 1.25-meter ham radio band. It is mainly used for FM communication through repeaters, although it is much less heavily used than the two-meter band.

225 to 400 MHz: This very wide band is used for military aviation communications in AM. Most channels are 100 kHz apart.

400 to 406 MHz: This range is used primarily by government and military stations in FM.

406 to 420 MHz: In the United States, this band is used exclusively by the federal government. All transmissions are in FM, with most channels spaced at 25 kHz intervals.

420 to 450 MHz: This is the 70-centimeter ham radio band, second in popularity to the two-meter band on VHF/UHF. The 420 to 444 MHz range is used for USB, digital modes, ham television, and ham communications satellites. The 444 to 450 MHz range is used for FM, mainly in conjunction with repeaters.

450 to 470 MHz: This is the "UHF" band on most scanners, used for many of the same purposes as the 30 to 50 and 150.8 to 174 MHz bands.

470 to 512 MHz: This is known as the "UHF-T" band, and covers the same frequency range as television channels 14 to 20. This band is used for many of the same purposes as the "UHF" band in areas of the country without television stations on those channels.

512 to 825 MHz: This range is where television channels 21 through 72 are located.

825 to 849 MHz: This range is used for cellular telephone service, with cellular units transmitting here. Listening in this range is prohibited.

849 to 851 MHz: This band is used to provide telephone service from aircraft in flight. SSB is generally used here. Listening in this range is prohibited.

851 to 866 MHz: This is used by many of the same users as the 450 to 470 MHz band, with channels spaced at 25 kHz intervals.

866 to 869 MHz: This allocation is used by public safety and law enforcement agencies.

869 to 894 MHz: This range is used for cellular telephone service, with cells transmitting here. Listening in this range is prohibited.

894 MHz and above: These higher frequencies are where new communications technologies, such as wireless local area networks, spread spectrum telephony, and direct satellite broadcasting are being implemented.

SCANNER

Terminology and Specifications

CTCSS: Continuous Tone Coded Squelch System (CTCSS, sometimes called .PL. for Motorola.s .Private Line. trademark) is a method of including a low-pitched tone in the transmission which trips the squelch on the intended recipient.s receiver(s), thus excluding the undesired signals from other users sharing the frequency. Some scanners now include the CTCSS capability so the listener can choose which service to monitor on a multi-user frequency.

Dynamic Range is the ability of a scanner to handle extremely strong as well as extremely weak signals without distortion or overloading. Since most scanners do this poorly, this specification is virtually never given.

Intermodulation ("intermod') is produced in the scanner circuitry when strong signal frequencies mix together, producing spurious signals on seemingly-unrelated frequencies. It is often recognized by its distorted sound, often containing mixed audio from multiple signals. Intermod is a consequence of inadequate dynamic range.

Images are produced in every receiver. They are recognizable as a duplicate of the legitimate signal, typically offset by 21.4, 21.6, or 21.7 MHz (twice the intermediate frequency--I.F.) from the actual frequency, depending upon the scanner. With up-conversion design, image frequencies may fall outside the tuning range where they aren't a problem.

Memory: The ability of a scanner to store favorite frequencies for scanning.

S.A.M.E. (Specific Area Message Encoding) Weather Alert: Your National Weather Service will alert you of weather and other emergencies for your county if programmed.

Scanning: The rapid sampling of memory-stored frequencies to find active frequencies. When the transmission ends, the scanning cycle resumes until another active frequency is found.

Searching: An automatic sweep between an upper and a lower frequency limit in a search for activity. When an active frequency is found, the search stops until the activity ends, then resumes.

Selectivity: The radio's ability to reject adjacent frequency interference; the sharper, the better, especially in strong-signal conditions. Average selectivity for a scanner is typically 30 kHz (+/- 15 kHz) at -50 dB.

Sensitivity: The weakest signal voltage that the radio will respond to audibly; the lower the number, the better. Good sensitivity is about 0.3-0.5 microvolts.

Priority Channel: Assigning a specific memory channel to be automatically sampled every few seconds for activity regardless of other functions currently running on the scanner.

Trunking: The automatic, equal sharing by several departments of a pool of frequencies. These frequencies often change between transmissions as the number of users increase or decrease.

VFO Control: A variable tuning control to allow continuous manual tuning up and down in frequency found on some scanners.